Catovirus sp. 'naegleriensis' Genome sequencing and assembly. Catovirus sp. 'naegleriensis'

Giant viruses (belonging to the Nucleocytoviricota) are significant lethality agents ofvarious eukaryotic hosts. Metagenomic studies showed that giant viruses are key players invirtually every environment. However, available giant virus isolates are limited to a minusculenumber of protist and algae hosts. Here we report on the first viral isolate replicating in theamoeboflagellate Naegleria. This genus includes the infamous human pathogen Naegleriafowleri, the causative agent of the rare but lethal disease primary amoebicmeningoencephalitis. We revealed the structure and infection cycle of Naegleriavirus (NiV),and show its unique adaptations to its Naegleria host by fluorescence in situ hybridization,electron microscopy, genomics, and proteomics. Naegleriavirus is only the fourth isolate ofthe subfamily Klosneuvirinae, a diverse group of viruses known mainly from metagenomicstudies. Like other Klosneuviruses, the genome of Naegleriavirus contains an unusually highamount of translation genes, yet it lacks tRNAs. NiV acquired genes from its Naegleria host,which code for heat shock proteins and apoptosis inhibiting factors, presumably for hostinteractions. Notably, NiV infection was lethal for all tested Naegleria species, including thehuman pathogen N. fowleri. This study extends our experimental framework for investigatinggiant viruses and could represent a first step toward the biological control of Naegleriafowleri.